Mixed activators for stabilized metathesis catalysts

ABSTRACT

A metathesis catalyst activator composition consisting essentially of an alkoxyalkylaluminum halide and a tin compound in a molar ratio of about 0.15 to 2 moles of the alkoxyalkylaluminum halide per mole of tin compound.

This application is a division of application Ser. No. 07/596,263, filedOct. 12, 1990, now U.S. Pat. No. 5,075,272.

This invention relates to the polymerization of dicyclopentadiene orother polycyclic cycloolefin or mixtures thereof under the influence ofa transition metal based ring-opening catalyst system. Specifically, itrelates to a new catalyst activator system which exhibits a high degreeof tolerance for air and moisture.

BACKGROUND OF THE INVENTION

Preparation of thermoset cycloolefin polymers via metathesis catalystsis a relatively recent development in the polymer art. Klosiewicz inU.S. Pat. Nos. 4,400,340 and 4,520,181 teaches a technique useful forpreparation of such polymers from dicyclopentadiene and other similarcycloolefins via a two-stream reaction injection molding techniquewherein a first stream, including the catalyst, and a second stream,including a catalyst activator, are combined in a mix head andimmediately injected into a mold where, simultaneously, polymerizationand molding to a permanently fixed shape take place.

In a system specifically taught by Klosiewicz, the ring-openingmetathesis catalyst is based on tungsten hexachloride or tungstenoxytetrachloride. It is also known that the corresponding molybdenumcompounds are effective ring-opening metathesis catalysts.

The tungsten or molybdenum catalyst is solubilized by complexing it witha phenolic compound so that a homogeneous catalyst/DCPD solution can beprepared. Also, in order to prevent premature ionic polymerization ofthe DCPD monomer in which the catalyst is to be dissolved, the catalystcomponent is stabilized by reacting it with a chelating agent or a Lewisbase. Such chelants as acetylacetone, dibenzoyl methane, andalkylacetonates, or Lewis bases such as benzonitrile or tetrahydrofurancan be employed as the stabilizer. The chelants and, particularly,acetylacetone (2,4-pentanedione), are preferred stabilizers.Stabilization of the catalyst prevents ionic polymerization, giving thesolution an almost indefinite shelf life in the absence of anyactivating mechanism taking place.

For a complete discussion of the preparation of such catalysts,reference can be made to Martin, U.S. Pat. No. 4,568,660.

Typically the stabilized catalyst is activated with an alkylating agentpossessing a high degree of Lewis acidity to strip off the stabilizingligand. The most frequently used activators for this purpose are thealkylaluminum or alkylaluminum halides. It is also known to use amixture of trialkylaluminum and dialkylaluminum halide. A preferredsystem is a mixture of di-n-octylaluminum bromide andtri-n-octylaluminum.

While these catalyst systems work very well and have been employed informulations which have been used in virtually all market penetrationmade to date by polymers of polycyclic cycloolefins, they sometimespresent handling difficulties due to their high degree of sensitivity toair and moisture. This is particularly true of the alkylaluminum halideactivators. These formulations must be protected from the atmosphere atall stages of handling, shipping, storage and use up to the time ofcharging into the mold.

This difficulty has been recognized and addressed in the art by Sjardijnet al, U.S. Pat. No. 4,729,976. Sjardijn discloses a catalyst systememploying an unstabilized WCl₆ /phenol complex, activated by a trialkylor triphenyl tin hydride. As also disclosed by Sjardijn, this activatoris quite insensitive to oxygen and moisture and, as a result, need notbe handled in an inert atmosphere. However, this system is not suitablefor use with stabilized catalyst complexes as it is not capable ofremoving the stabilizing ligand from the tungsten. Further studies haveindicated that other known tin compounds behave similarly.

BRIEF STATEMENT OF THE INVENTION

In accordance with this invention there has been found a ring-openingmetathesis polymerization catalyst system including a mixed aluminum/tinactivator which has a high degree of tolerance to oxygen and moisturebut has sufficient Lewis acidity to strip away the stabilizing ligandfrom a stabilized tungsten or molybdenum salt catalyst component.Following removal of the stabilizing ligand, the tin compound is a verysatisfactory activator.

Briefly stated the invention is a metathesis catalyst activatorcomposition consisting essentially of a tin compound and analkoxyalkylaluminum halide in a molar ratio of about 0.15 to 2 moles ofalkoxyalkylaluminum halide per mole of tin compound.

DETAILED DESCRIPTION OF THE INVENTION

The activator system contemplated by this invention is made up of a tincompound which is a non-Lewis acid activator and a Lewis acid which is,at best, an extremely weak activator after its Lewis acid functionalityis exhausted. In fact, Minchak, in U.S. Pat. No. 4,426,502 teaches theuse of alkoxyalkylaluminum compounds as activators (referred to byMinchak as cocatalysts) in metathesis polymerization using ammoniumalkyl molybdate or tungstate catalysts. This system is, by design, avery slow acting system seeking to take advantage of this very lowactivating action of the alkoxy alkylaluminums. For most commercialpurposes, much faster action is required and for these applications,alkoxyalkylaluminums are not considered to be satisfactory activators.

In this invention, alkoxyalkylaluminum halides are employed as Lewisacids. Such compounds have the general formula (RO) R'Al where R is analkyl radical having 1 to 18 preferably 2 to 4 carbon atoms, or a phenylradical, R' is an alkyl radical having 1 to 18 preferably 2 to 4 carbonatoms, and X is a halide radical, preferably chloride or iodide. Aparticularly preferred species is ethyl, n-propoxyaluminum chloride [C₂H₅ (C₃ H₇ O)--AlCl]. Other specific examples are ethylethoxyaluminumchloride, ethylisopropoxyaluminum chloride, methyl ethoxy aluminumchloride, propylethoxyaluminum chloride, ethylpropoxyaluminum iodide andethyliodide.

The tin compound of the mixed activator can be any tetravalent tincompound that is used with unstabilized tungsten or molybdenumsalt-based activators such as, e.g. alkyltin hydrides, aryltin hydrides,tetraalkyltin compounds, hexaalkyl and hexaaryl di-tin compounds, andalkyltin halides. Alkyltin hydrides useful in this invention have thegeneral formula

    R.sub.3 --Sn--H

where R is a straight or branched chain alkyl of 1 to 10 carbon atoms.The preferred embodiment is tributyltin hydride. The preferred aryltinhydride is the phenyl analog.

Tetraalkyltin compounds having 1 to 5 carbon alkyl substituents are wellknown for use as activators for olefin metathesis but are not effectivewith the stabilized tungsten and molybdenum salt catalyst systems. Theyare effective in combination with the alkoxyalkylaluminum halides ofthis invention. The preferred tetraalkyltins are tetramethyltin andtetrabutyltin.

Hexaaryl and hexaalkyl di-tin compounds have the general formula

    R.sub.3 --Sn--Sn--R.sub.3

where R is a phenyl group or an alkyl group of 1 to 5 carbon atoms. TheR substituents can be the same or different. Preferred examples of thisembodiment are hexamethyl, hexabutyl or hexaphenyl di-tin.

The alkyltin halides that can be used in this invention have the generalformula

    R.sub.n SnX.sub.(4-n)

where n is 1 to 3 and R and X are as defined hereinabove.

The operative ratio of the alkoxyalkylaluminum chloride to tetravalenttin compound is between about 0.15 and about 2. Below this range, thetime required to cure dicyclopentadiene to a crosslinked, fully curedproduct is greater than is commercially practical. Above this range, thedegree of polymerization falls off as demonstrated by increased levelsof unreacted monomer in the resultant polymer.

The invention is of use in the polymerization of polycyclic cycloolefinmonomers generally, and in particular, in the polymerization of suchmonomers in bulk i.e. in the absence of solvent. Such monomers include,by way of example--,--dicyclopentadiene, higher cyclopentadieneoligomers, norbornene, norbornadiene, 4-alkylidene norbornenes,dimethanooctahydronaphthalene, dimethanohexahydronaphthalene, adducts ofthese monomers with monocyclic cycloolefins and substituted derivativesof these compounds. The preferred cyclic olefin monomer isdicyclopentadiene or a mixture of dicyclopentadiene with otherpolycyclic cycloolefin monomers in ratios of 1 to 99 mole % of eithermonomer, preferably about 75 to 99 mole % dicyclopentadiene.

The invention is illustrated in the following nonlimiting examples.Parts and percentages, unless otherwise stated, are by weight.

In these examples, ethylproxyaluminum chloride (EPAC) was prepared byreaction of one equivalent of n-propanol with one equivalent ofdiethylaluminum chloride (DEAC). A nitrogen-sparged 4" polymerizationtube, capped with an extracted rubber liner and equipped with a bubblerfilled with mineral oil, was charged with 2.78 ml 1.8M DEAC in toluene.To this was added 6.85 ml dry toluene. Next was added 0.37 ml n-propanol(carefully by syringe), giving the rapid evolution of gas. Heat was alsoevolved. The solution was 0.5 M in Al and was used without furthermanipulation.

In carrying out bulk molding by metathesis polymerization ofcrosslinking systems, two parameters are important. When the liquidstreams are first mixed, a short induction time is observed, followingwhich reaction begins and a rapid viscosity build-up takes place to apoint at which the material becomes too viscous to be pumped to a mold.This time interval is known as the gel time. When the gel time isreached, the liquid must be in the mold. Shortly following gel time avery rapid temperature increase is observed as the remainder of thepolymerization and the bulk of the crosslinking takes place. The timefrom mixing to attainment of 100° C. is arbitrarily taken as thepolymerization time (cure time) although the temperature rise continuesto 175° C. and higher.

GENERAL POLYMERIZATION PROCEDURE

Polymerizations were carried out in sparged 15×125 mm test tubes whichwere stoppered with rubber stopples secured with electrical ties.Disposable syringes and needles were sparged before use and used onlyonce. For polymerizations with catalyst (B) and activator (A)components, the test tube was charged with 2.0 ml of the catalystcomponent. Next, a thermocouple attached to a digital thermometer wasinserted. The desired starting temperature (33±2) was obtained byheating with a heat gun. Finally, 2.0 ml of the activator component wasrapidly injected and a stopwatch was started. Mixing was accomplished byvigorous shaking. The gel time (t_(gel), seconds) was taken at the timewhen the mixture ceased to flow readily upon inversion of the tube. Thecure time (t₁₀₀, seconds) was taken as the time to 100° C., except forthose polymerizations started at 50° C. and higher, where the time to110° or 120° C. (t₁₁₀ or t₁₂₀) was sometimes used. (Since the rate oftemperature rise is so rapid during the exotherm, there is very littledifference in cure times regardless of which temperature is used.) Theinitial (T_(o)) and maximum temperatures (T_(f)) were recorded tocalculate the exotherm (T_(exo)) i.e. the difference between T_(o) andT_(f).

EXAMPLE 1

In this example, polymerizations were carried out using tributyltinhydride (TBTH) as the catalyst activator. A 0.5M catalyst solution wasprepared by slurrying one equivalent of WCl₆ in chlorobenzene under anitrogen atmosphere. To this slurry were added, sequentially, 0.25equivalent of t-butanol, 1 equivalent of 2,6-diisopropylphenol and 2equivalents of acetylacetone (2,4-pentanedione). A solublediisopropylphenol complex of mixed WCl₆ /WOCl₄, stabilized to deactivateit as an ionic DCPD polymerization catalyst, resulted. The complex wasdissolved in DCPD to form a 0.0074M tungsten concentration.

A series of activator solutions in DCPD was prepared having a standardTBTH concentration of 0.22M. To these were added varying amounts ofethylpropoxyaluminum chloride (EPAC).

Following the general polymerization procedure described above, a seriesof polymerizations was carried out using equal quantities of thecatalyst and activator solutions. The ratio of tin to tungsten in thereacting mass was held constant at 3/1. The ratio of aluminum totungsten was varied from 0.5 to 3.5 and the polymerization (cure) timewas measured. Data from these runs are recorded in Table 1 as is also acontrol (std) run using, as the activator, a mixture of trioctylaluminumand dioctylaluminum iodide.

                  TABLE 1                                                         ______________________________________                                        Al/W      T.sub.exo                                                                            t.sub.100  DCPD  % Swell                                     ______________________________________                                        0.5       180    207        1.51  52.1                                        1.0       177    118        0.93  53.4                                        1.5       188    72         0.75  57.1                                        2.0       193    42         0.74  56.5                                        2.5       176    30         0.87  55.9                                        3.0       188    29         0.53  105.8                                       3.5       186    30         1.02  101.0                                       std       188    36         0.78  109.8                                       ______________________________________                                    

From the above, it can be seen that as the aluminum to tungsten ratioapproaches 2, the cure time decreases to a practical point at which itthereafter remains essentially constant. It will be noted that thisratio is also the ratio of the acetylacetone to tungsten in the catalystcomplex. From the table it can also be seen that little or no activationtakes place with either TBTH or EPAC, used alone.

EXAMPLE 2

Using the same polymerization techniques, another series ofpolymerizations was carried out wherein the Al/-W ratio was heldconstant and the Sn/W ratio was varied. Here, cure times decreased withincreasing tin concentration, but polymerization efficiencies decreasedas tin concentration increased as evidenced by the residual DCPD in thepolymer (column headed DCPD). Data are presented in Table 2.

                  TABLE 2                                                         ______________________________________                                        Sn/W      T.sub.exo                                                                            t.sub.100  DCPD  % Swell                                     ______________________________________                                        3/1       188    43         1.28  53.9                                        6/1       176    31         9.29  47.5                                        10/1      159    27         13.32 48.6                                        2/1       191    39         1.90  43.9                                        1/1       195    67         0.62  39.1                                        ______________________________________                                    

EXAMPLE 3

To demonstrate the tolerance to air of the mixed TBTH/EPAC activatorsystem, a series of DCPD polymerizations were run, as in Example 1,wherein TBTH/EPAC activator solutions were initially treated with dryair at a level of about 0.25 mole of 0₂ per mole of Sn. In theseactivator solutions the ratio of DCPD to TBTH was held constant at1000/3 and EPAC concentration was varied. These were combined with acatalyst-containing component wherein the DCPD/tungsten ratio was heldconstant at 1000/1. Thus the reacting solution was DCPD/W/Sn at a ratioof 2000/1/3. Polymerizations were carried out via the generalpolymerization procedure described above. Results are presented in Table3.

                  TABLE 3                                                         ______________________________________                                        Control         15 minutes* 72 hours*                                         Al/Sn   t.sub.100                                                                            DCPD     T.sub.100                                                                          DCPD   t.sub.100                                                                           DCPD                                ______________________________________                                        0.5     207    1.51     373  2.76   497   3.22                                1.0     118    0.93     170  0.94   251   1.41                                1.5     72     0.75     80   0.95   260   1.88                                2.0     42     0.74     66   0.74   160   1.35                                2.5     30     0.87     33   0.82   148   1.02                                3.0     29     0.53     33   0.56   124   0.76                                3.5     30     1.02     38   0.74    94   1.52                                std     36     0.78     58   0.55   7200  --                                  ______________________________________                                         *time after exposure to air                                              

In the data presented above, the control is a run carried out using theactivator prior to exposure to air. The "STD" is a conventionalactivator containing no TBTH and no EPAC but, rather, containingDCPD/trioctylaluminum/dioctylaluminum iodide/diglyme at 1000/3 DCPD/Alratio.

The improved resistance to air of the mixed activator is manifest.

COMPARATIVE EXAMPLES

In this example, experiments were performed that demonstrate the pooractivation results obtained using EPAC or TBTH alone to activate astabilized catalyst.

All polymerizations were carried out using catalyst prepared as inExample 1, except that the solvent was toluene and the phenol wasnonylphenol in place of 2,6-diisopropylphenol. The final monomer (DCPD)to catalyst ratio was 2000/1. Polymerizations were done at an initialtemperature of 33°±2° C., following the procedure of Example 1. Resultsare presented in Table 4 where the amounts of TBTH and EPAC are moleratios relative to tungsten.

                  TABLE 4                                                         ______________________________________                                                                          %    %    %                                 TBTH  EPAC     t.sub.gel                                                                            t.sub.100                                                                           T.sub.exo                                                                           gel  swell                                                                              DCPD                              ______________________________________                                        3     0        no gelation or                                                                polymerization                                                 3     3        5 sec  130   180° C.                                                                      100  57   2.47                              0     3        no gelation or                                                                polymerization*                                                ______________________________________                                         *When heated to 75° C., this mixture polymerized in about one hour     to give a polymer with swell 144% and residual monomer 0.62%.            

In carrying out the process according to this invention, otherprocessing refinements employed in the presently practiced commercialtechnique can be used. For example, additives to reduce the unreactedmonomer content can be present. Also fillers and reinforcing aids can beadded, as well as antioxidants and stabilizers.

These additives are added to the starting solutions, since at least inthe case of DCPD they cannot be added after the solutions arepolymerized. Such additives may be added in either the catalyst streamor the activator stream or both. The additives should be substantiallyunreactive with the catalyst or activator component in the solutions andthey must of course have substantially no inhibitory action topolymerization. If a reaction between the additive and the catalystcomponent or the activator component is unavoidable, but does notessentially inhibit the polymerization, the additives can be mixed withthe monomers to prepare a third solution, and the third solution can bemixed with the first and/or second solutions immediately beforepolymerization. When the additive is a solid filler having intersticesbetween particles which can be filled sufficiently with the mixedsolution immediately before or during the polymerization reaction, themold can be filled with the filler prior to charging the reactivesolutions into the mold.

In order to decrease the residual monomer content, a small amount of anactive halogen compound such as trichloromethyl toluene,dichlorodiphenyl methane, ethyl trichloroacetate, or isophthaloylchloride or an acid anhydride such as benzoic anhydride may be added.

A variety of additives may be included in the formulations of thepresent invention to improve or to maintain characteristics of moldedarticles prepared therewith. Additives include fillers, pigments,antioxidants, light stabilizers, flame retardants, macromolecularmodifiers and the like. The reinforcing materials or fillers used asadditives can improve the flexural modulus of the polymer. These includeglass fibers, mica, carbon black, wollastonite and the like.

The molded polymer prepared in the present invention should also containan antioxidant in most cases. Preferably, a phenolic or amineantioxidant is added to the solutions prior to polymerization. Examplesof the antioxidants include 2,6-t-butyl-p-cresol,N,N-diphenyl-p-phenylenediamine, andtetrakis[methylene(3,5-di-t-butyl-4-hydroxycinnamate)]-methane.

In some embodiments of this invention, a preformed elastomer which issoluble in the reactant streams is added to the metathesis-catalystsystem in order to increase the impact strength of the polymer. Theelastomer is dissolved in either or both of the reactant streams in anamount from about 3 to about 15 weight percent range, based on theweight of monomer. Illustrative elastomers include natural rubber, butylrubber, polyisoprene, polybutadiene, polyisobutylene, ethylene-propylenecopolymer, styrene-butadiene-styrene triblock rubber, randomstyrene-butadiene rubber, styrene-isoprene-styrene triblock rubber,ethylene-propylene-diene terpolymers and nitrile rubbers. The amount ofelastomer used is determined by its molecular weight and is limited bythe viscosity of the resultant reactant streams. The resultant reactantstreams containing elastomer cannot be so viscous that mixing is notpossible. Although the elastomer can be dissolved in either one or bothof the streams, it is desirable that it be dissolved in both.

What is claimed is:
 1. In a process for polymerizing a polycycliccycloolefin wherein a plurality of liquid streams, at least one of whichcontains a polycyclic cycloolefin and a metathesis polymerizationcatalyst and at least one of which contains a metathesis polymerizationcatalyst activator are brought together and substantially immediatelyinjected into a mold where polymerization and molding take placesimultaneously, the improvement which comprises said catalyst being atungsten or molybdenum salt stabilized against ionic polymerization andthe activator being a mixture of an alkoxyalkylaluminum halide and a tincompound selected from the group consisting of alkyltin hydrides,aryltin hydrides, tetraalkyltin compounds, hexaalkyl and hexaaryl di-tincompounds and alkyltin halides in a ratio of about 0.15 to 2 moles ofalkoxyalkylaluminum halide per mole of tin compound.
 2. The process ofclaim 1 wherein the alkoxyalkylaluminum halide is ethylpropoxyaluminumchloride and the tin compound is a trialkyltin hydride.
 3. The processof claim 2 wherein the trialkyltin hydride is tributyltin hydride.